Lasers beams with a non-Gaussian intensity profile such as super-Gaussian, Airy or doughnut-like can be preferable in some applications, such as laser materials processing, medicine and so on. The Applicant believes that a non-Gaussian laser beam power density distribution may result in a significant reduction of the powder consolidation zone. Additionally, the penetration into the substrate of the working platform using flat-top laser beam profile has better results for single track formation.
Methods of shaping and producing such non-Gaussian beams can be divided into two classes, namely extra- and intra-cavity beam shaping. Extra-cavity (external to the laser cavity) beam shaping is realised by manipulating an output beam from a laser with suitably chosen amplitude and/or phase elements [1]. Unfortunately, extra-cavity beam shaping results in unavoidable losses, while reshaping the beam by phase only elements suffers from sensitivity to environmental perturbations. Additionally, current methods may have serious unsolved problems with reshaping of incoherent laser beams. In order to solve the problem, amplifiers with shaped gain profiles may be used.
The second method of producing such beams is intra-cavity (within the laser cavity) beam shaping. The efficiency of this method can be quite high by means of maximising a laser pump and output mode overlap while producing the required beam [2-3]. A disadvantage of this method is a complexity of the intra cavity optics involved [3]. The Applicant notes that these methods usually do not allow adaptive control of the output beam.
The Applicant wishes to obtain adaptive manipulation of a transverse gain structure to control a transverse intensity distribution of an output beam in laser system. An output beam of such laser may be able to vary both an output power and transverse intensity distribution simultaneously.